(552f) The EFFECT of COAL Composition ON Ignition and Flame Stability IN CO-Axial Oxy-FUEL Turbulent Diffusion Flames

Past research on flame stability and stand-off distance under oxy-coal combustion conditions has used a 100kW pulverized coal test rig with a co-axial turbulent diffusion burner, and has been described at previous Pittsburgh Coal Conferences. These studies were for one specific coal, namely a Utah Bituminous Coal. The purpose of the research described in this paper is to extend the previous work and to explore how coal composition changes affect the following dependencies that control flame stand-off distance and flame ignition, namely: 1) the effect of partial pressure of oxygen (PO2) in the primary stream with differing preheat temperatures in the secondary stream; and 2) the effect of PO2 in the secondary stream with zero O2 in the primary stream. The results of this new study were designed to extend previously obtained knowledge on effects of secondary preheat temperature, turbulent mixing, PO2 in various streams, from one single coal to other coals of differing compositions.

This paper, therefore, explores the effects of coal composition on ignition in oxy-coal, coaxial, turbulent diffusion flames. In this research, the stability and stand-off distance of the flame were studied for the following three types of coal: Utah Skyline Bituminous, Illinois #6 Bituminous, and a Powder River Basin (Black Thunder) coal. To this end we investigated: 1) the effect of PO2 in the primary stream, 2) the effect of PO2 in the secondary stream, and 3) the effect of preheat temperature in the secondary stream, on flame stand-off distance, using the same photo-imaging methodology described elsewhere. The results of the ignition and flame stability analysis for these three coals under oxy-firing conditions are compared, and the effects of coal composition are elucidated.